1. Field of the Invention
This invention relates generally to a pressurized filter and backwashing apparatus. More specifically, a granular pressure sensitive filter and a backwashing apparatus and method using filtered liquid under pressure is disclosed.
2. Description of the Prior Art
Granular filters are very effective in removing solid material from a liquid flow. However, the filter looses usefulness as it becomes impaired by the deposition and entrapment of filter clogging material. The success of any granular filter depends on the ease and on the extent which the filter can be cleaned. Granular filters also rely on influent water to pass through the filter and into a pipe. The pipe is constructed with slits for gathering the filtered water. These slits must be small enough to prevent the sand from gaining entrance, yet large enough for the fluid to pass.
The prior art utilizes numerous structures and flow patterns in order to enhance the ease and extent a clogged filter can be made useful. In an early process an outer portion of a rotatable cylinder comprising an inner and outer wire mesh cylinder which holds a filtering material between the wire mesh cylinders enables the influent to flow into the interior of the rotatable drum through the filtering medium and into a reservoir as cleaned water. As the filtering medium begins to clog, the level of influent water within the drum rises to trigger a motor which rotates the drum filtering means. Effluent cleaned water is then pumped from the effluent reservoir and sprayed upon the filtering means to wash it free of the clogging material. The contaminated backwash water is directed to an outflow by means of a trough within a cylinder. As the influent level falls the rotatable cylinder stops rotating thereby ending the backwash process.
In another prior art process for cleaning a sand filter, the water to be clarified passes upward through a sand filter and accumulates above the sand filter as clarified water which is allowed to drain off. For cleaning the sand filter, the process was essentially reversed.
In another process, a specially designed gravity filter apparatus prevents the filtering material from passing along with the effluent during the backwashing process. The backwashing process utilizes a washing liquid generally a water and gas mixture and passes this mixture upward through the filter to create a water-gas emulsion which loosens the clogging material from the filter.
In another gravity sand filter, the backwashing process utilizes a backwash fluid comprising water or water with air which is pushed up through the filter and removed from the filtering apparatus by overhead troughs.
The prior art systems are complex in structure, difficult to use and allow a portion of the filter clogging material to fall back onto the filter surface after the backwashing process.
It is a primary object of this invention to provide a filter and backwash apparatus and method which permits the filtered liquid to be used directly for backwashing the filter cell and filter tank.
It is a further object of this invention to provide a filter and backwash apparatus which is simple in design and economical to operate.
It is a further object of this invention to provide a filter and backwash apparatus which utilizes relatively a small amount of filtered water in the backwashing process.
It is a further object of this invention to provide a filter and backwash apparatus which is simple to operate.
It is a further object of this invention to provide a filter and backwash system which cleans the filtering medium and filter tank during the backwash process.
It is a further object of this invention to provide a filter and backwash process capable of manual or automatic backwash initiation and termination.
It is a further object of this invention to provide a filter cell which enables radial filtration and radial backwashing about the length of the filter cell.
It is a further object of this invention to provide a backwashing apparatus which prevents the clogging material removed from the filter cell and filter tank by backwashing to settle back onto the filter cell or back into the filter tank.
The effectiveness and time of backwashing is related to the amount of water which flows out of the collection tube and back through the filter element. This, in turn, is controlled by the opening size of the holes or slits in the tube. For back washing large openings are desirable. However, as discussed previously, if the opening is too large, sand will clog the opening and the system will not perform properly.
It is a still further object of this invention to provide a filtration element which can allow filter water to pass through it while still allowing back flow washing.
It is a further object of this invention to provide a filtration element which has a collection tube allowing varying amounts of liquid to pass into or out of the tube.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed to be merely illustrative of some of the more pertinent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention is a different manner of modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description describing the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.